title: Isotenulin.
abstract: Isotenulin, C17H22O5, is a sesquiterpene lactone isolated from sneezeweed Helenium amarum. It crystallizes with two independent mol-ecules in the asymmetric unit. In each mol-ecule, two five-membered rings (cyclo-pentenone and lactone) are trans-fused to the central seven-membered ring. The five-membered rings each adopt envelope conformations. The seven-membered ring adopts a twist-chair conformation. In the crystal, the molecules are linked by C-H⋯O interactions, which generate a three-dimensional network.
authors.affiliation: Department of Chemistry, The University of Tennessee at Chattanooga, Chattanooga, TN 37403, USA.
authors.forename: Kyle S
authors.initials: KS
authors.lastname: Knight
authors.forename: Cole T
authors.initials: CT
authors.lastname: Smith
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Waddell